Question

If a body looses half of its velocity on penetrating 3 cm in a wooden block, then how much will it penetrate more before coming to rest?
A. `1 cm`
B. `2 cm`
C. `3 cm`
D. `4 cm`

Answer 1

Correct Answer - A
Let initial velocity of body at point `A` is `v, AB` is `3cm`.

From `v^(2) = u6(2) - 2as`
`((v)/(2))^(2) = v^(2) - 2a xx 3`
`a = v^(2)/(8)`
Let on penetrating `3cm` in a wooden block, the body moves `x` distance from `B` to `C`.
So, for `B` to `C`
`u = (v)/(2), v = 0`,
`x = x, a = (v^(2))/(8)` (deceleration)
`:. (0)^(2) = ((v)/(2))^(2) - 2. (v^(2))/(8).x`
`x = 1`